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brantlew wrote:... You can tighten the radius up a bit, but you will start noticing the turn more. I can imagine some people would just tolerate the turn as a necessary compromise to fit within a small space but it does break the immersion a bit. Different content can make a difference though. Something like Skyrim just begs for long extended walking sequences so it would be difficult to do in a basketball court without you feeling like a pinball, but I can imagine slower paced indoor environments working pretty well in a small area. However, GPS has the inverse problem of optical - it doesn't work very well for small spaces. A basketball court is just about the minimum size you can go, and only if your GPS signal is rock solid.

On a related note: my father owns a small ranch, and I was able to test Red Rovr once on about a 4 acre region. Other than the weeds and cow turds - it was a pretty cool experience never feeling a turn and never hitting a boundary.

PS. Blind walking is dangerous enough on a featureless field. Adding other blind people to the mix sounds like a disaster waiting to happen

And for multi-player, it used GVS to do collision avoidance and boundary enforcement, to keep people at a safe distance from one another.

Without GVS I could see it being too small to maintain immersion, and certainly not safe for multiple players. From what I read elsewhere, a football field is about the right size for non-GVS directed walking, which agrees with your findings.

I suppose for a custom VR environment you could put in virtual obstructions that match obstructions in the outside world, so the boundary enforcement would not feel so artificial. Of course that is a no-go for existing commercial games.

I can't wait to try this out myself. But first I have to get a backtop ready. It would be interesting to see what can be done with a Nexus 7 and a pair of lenses for a DIY solution that can do directed walking without a backtop computer. The internal IMU sensors may be okay if quick turns are avoided.

Something I try to avoid is dismissing new ideas because they don't immediately look practical, especially if I haven't tried it or know the background info the developers have. I have to admit to struggling a bit with free-walking because of the need for space and weather and feeling self-concious but I'm starting to see potential.

Free-walking the dog
If you're getting bored of the same route every day it's feasible to think of combining it with some virtual tourism.

Getting more from public playing fields
Most of these seem to remain unused for most of the week. How about if rather than overlapping you divided the pitch up into squares so all the players had their own space? This might suit some games and VR activities and not all the players would even need to be in the same game, they could all be online.
Normal park lighting rather than flood lighting would do at night. The spaces could dynamically change size according to game content or the number of people turning up.

Flassan wrote:Getting more from public playing fields
Most of these seem to remain unused for most of the week. How about if rather than overlapping you divided the pitch up into squares so all the players had their own space? This might suit some games and VR activities and not all the players would even need to be in the same game, they could all be online.
Normal park lighting rather than flood lighting would do at night. The spaces could dynamically change size according to game content or the number of people turning up.

That seems like the safest way to do it - segmenting the field into zones. For cooperative play like squad-based scenarios I think it would be possible to keep players within proximity of each other. It would be a bit tricky because you would be redirecting the group as a unit, but they would all remain in the same reference frame and so within their little "bubble" they would be able to interact with each other.

@geekmaster: I'm not exactly sure how you would use GVS effectively. The woman in the video is clearly aware of the sensation and feels out of balance so that seems far above the threshold for comfortable steering. You would need something below the threshold of perception which would yield a much larger radius - and still I'm a little skeptical of being able to move someone continuously through imbalance without inducing feelings of nausea. But I admit I'm not that familiar with GVS. I do think one interesting possibility however could be simulating terrain. It is distracting to walk on a flat surface while being presented with a virtual slope. If you could use GVS to tilt your sensation of gravity then that might be an interesting way to simulate slopes. But then again - you might just induce falls as the person trusts their instincts and leans away from their true center of gravity.

brantlew wrote:... If you could use GVS to tilt your sensation of gravity then that might be an interesting way to simulate slopes. But then again - you might just induce falls as the person trusts their instincts and leans away from their true center of gravity.

I know that feeling. There was a time in my life where I had vestibular problems. I would be walking or standing perfectly still, and suddenly the room rotated and the floor came up and slapped me in the head. It took some time to learn to ignore my natural balance and use my eyesight instead, to keep from falling. GVS could simulate my experience (but in a padded room for safety).

[quote="geekmaster"]The experiments using a basketball court also used Galvanic Vestibular Stimulation, such as this:
[youtube]http://www.youtube.com/watch?v=oefVaHDo5xg[/youtube]
Some demo videos risk doing more harm than good in that they're informative if you know about the subject but baffling to everyone else. I love this video but it appears to show a radio controlled Zombie. Are there any good articles that might convince me about GVS?

@Flassan: Terrain simulation is one area where ODT clearly win out. While being quite complex, it is at least possible to mount a treadmill on a 2DOF motion platform to vary the slope. There just isn't any comparable solution with free walking.

I feel compelled to bring up this post again from a long time ago which may have been missed. Basically it's an idea for a mechanical redirection machine. Looking back at the idea, I wonder if combining both mechanical and visual redirection together could tighten the size requirement down to something manageable. Not something that would fit in a house, but maybe something like half a basketball court that could be realistically constructed and in easy range of optical tracking.

@brantlew. That's great idea. Don't know if it would ever be practical but any ideas are good because they lead to further ones.
What would happen if you used lots of smaller circles instead? They would be easier to fabricate and require lower torque motors. Each one would turn you a small amount.
Would they cope with strafing better? Could more than one person sometimes use it?

Flassan wrote:... Some demo videos risk doing more harm than good in that they're informative if you know about the subject but baffling to everyone else. I love this video but it appears to show a radio controlled Zombie. Are there any good articles that might convince me about GVS?

Although known about for 100 years or so, galvanic vestibular stimulation attracted relatively little interest until some 15 years ago. ... The stimulation technique is very simple. The only apparatus required comprises a 9 V battery, a switch and a means of controlling the current. A small current (around 1.0 mA) passed between the mastoid processes for a second or two will cause a person to sway if they are standing with their eyes closed. ... the direction of the evoked movement was always in the direction of the anodal ear. ... the electrically evoked vestibular input is capable of perturbing a complex motor process, one that is able to take into account the relative positions of all body segments from the head to the feet. ... the evoked vestibular input is capable of influencing more than one whole-body control process. ... if a person performs a voluntary movement of the upper body the stimulus produces an additional effect by modifying the movement itself ... the vestibular input also gains access to those motor processes that control voluntary movement. ... an additional central process may be affected by the stimulus.

A patient undergoing GVS noted:
I felt a mysterious, irresistible urge to start walking to the right whenever the researcher turned the switch to the right. I was convinced — mistakenly — that this was the only way to maintain my balance. The phenomenon is painless but dramatic. Your feet start to move before you know it. I could even remote-control myself by taking the switch into my own hands.

Luckey wrapped up his session by considering where virtual reality will go next, highlighting galvanic vestibular stimulation – where electrodes are used to interact with the inner ear in order to produce the sensation of inertia – as one possibility. It might not be quite as far away as we think, either. Luckey is, at least in terms of public awareness, leading the charge for virtual reality headsets, and he’s already turning his attention to GVS.

“It’s really cool, and I’ve put some GVS systems together myself,” he enthuses with the wide-eyed smile of someone who’s less bothered about his own safety than others. “The problem is, it’s not particularly safe. I mean, there’s no evidence that it’s bad for you to hook up electrodes behind your ear and send shocks into the body… but there’s no evidence that it isn’t, either…”

Who knows? Perhaps a future model of the Oculus Rift will have built-in GVS. Cool!

Sadly, although GVS research is more than 100 years old, there are patents regarding various aspects of using GVS inside VR, so the Rift GVS may need to be provided as a kit (some assembly required)...

One good thing about the information contained in those patents is the reassurance that GVS helps to reduce or eliminate VR motion sickness by making the visual and vestibular senses agree with one another. So it should also magnify the effects of directed walking to allow operating in a smaller playing field, as mentioned previously.

Thanks for all the information @geekmaster. I'm very glad to have a better understanding of it.
It may just be my impression but they don't seem to have got that far with it except to prove you can use a relatively high voltage to interfere with your body's tiny and highly complex electrical impulses. I see that ProfVR suggested caution and would have to agree. Mind you, if they do come up with a safe device that enhances sensations or neutralises nausea I would certainly try it.

Going back to @brantlew's Turntable ODT idea actually who knows what's practical given a military/Hollywood/medical budget?
This is the sort of thing I meant. It's high end but is scaleable and reusable as well as being feasible to make, transport and store. It would be hard to predict how good it would be without building it. The speed you walk at and how large you make it would impact on how often boundary enforcement occurs.

Multi turntable ODT.png

I heard that without a reference you cannot walk in a straight line and actually walk in a circle with a diameter of about 200 metres, which would mean that after 2/3 Km you arrive back in the same place (it might be that your rate of change of direction equates to that). For those who haven't come across it Re-directed walking in CAVEs rotates the image imperceptibly and exploits head-movements to prevent people facing the rear and is used when there are only 3 walls. The same technique could reduce the overall area needed.

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I think this is a really good idea Flassan. Much easier to build and also modular. The only issue would be that there are lots of "cracks" between the disks so your external tracker would need to be very good at detecting the precise placement of your feet. You might not want to rotate a disk if your foot was only halfway on it. The larger the disks, the less of a problem it would be but hopefully there would be a "sweet-spot" between practicality and performance - maybe a meter diameter?. Another nice aspect of this solution is that it solves the problem of the inactive wedges between the larger disks. Effectively the entire floor surface could be "tiled" with these disks.

I think for a prototype you could build a small set of 2 or 3 disks and then line then up and test how it feels stepping from one to the next, stepping on the cracks, etc.. Also you could form partial curves with them and test what radius of redirection you could expect to achieve comfortably.

I had an idea for a different kind of redirected motion treadmill a while back. I don't have time to make a drawing right now, but essentially, the idea was to have a very WIDE treadmill with a belt that can rotate forward or backward. The redirection aims the player towards the front or rear of the treadmill. The wide belt gives room for the redirection. It's a really nice and simple solution, but whether or not it would work rests on how wide the belt must be.

I don't have a particularly good guess, but based off playing with RedRoVR for a little bit, I would guess upwards of 15' wide at a bare minimum, including lots of level design tricks to support redirected motion.

brantlew wrote:I think this is a really good idea Flassan. Much easier to build and also modular. The only issue would be that there are lots of "cracks" between the disks so your external tracker would need to be very good at detecting the precise placement of your feet. You might not want to rotate a disk if your foot was only halfway on it. The larger the disks, the less of a problem it would be but hopefully there would be a "sweet-spot" between practicality and performance - maybe a meter diameter?. Another nice aspect of this solution is that it solves the problem of the inactive wedges between the larger disks. Effectively the entire floor surface could be "tiled" with these disks.

A thought I had was it might simply take advantage of when you stop to turn you around and point you back at the centre. I think any kind of moving platform or wheeled footwear is probably a challenge to use if you sense the 'ground' moving beneath you.
You could include "lots of level design tricks to support redirected motion". I was thinking that in theory if the game knew where you were standing it could put things in your way to stop you when necessary and even subtly dynamically alter the position or doorways and terrain when you weren't looking in order to maintain your optimum position.

RTK tech like this could be useful for a freewalking vr system.http://www.kickstarter.com/projects/swi ... n=398b4977
Campaign not yet live.
If it's that accurate accelerometers would only be needed for the first second of movement, and you could easily detect crouching for free (once ground slope is calibrated).

shole wrote:RTK tech like this could be useful for a freewalking vr system.http://www.kickstarter.com/projects/swi ... n=398b4977
Campaign not yet live.
If it's that accurate accelerometers would only be needed for the first second of movement, and you could easily detect crouching for free (once ground slope is calibrated).

My thoughts as well.

The first incarnation of Red Rovr (the one on the basketball court video) used GPS exclusively. It was laggy and glitchy, but it worked well enough to prototype the concept. Centimeter accuracy could be very interesting - still not enough for head positioning and such but enough to allow for subtle character movements far beyond the capabilities of the current inertial system. Of course this assumes a reasonable latency level and persistence accuracy. Probably no good if your accuracy varies greatly. The GPS version of Red Rovr had this annoying habit of occasionally just moving the character up to several meters in a random direction when the positional accuracy failed - even if you were standing still. It sometimes felt a lot like walking around massively drunk.

Re the kickstarter 1cm GPS... is it necessary to even use satellite based GPS with this technique?

I was wondering if the GPS satellites could be replaced with ground based transmitters, then use the same technique to get decent accuracy. That way, this would be a solution for indoors (GPS signals dont penetrate buildings very well).

Krenzo's project may be a better solution for something like this, compared to terrestrial GPS. GPS is time-of-flight, which means that you need multiple base stations with highly-accurate and synced clocks. In his method, he's measuring the phase difference between 4 antennas on his sensor, so I think that the base stations do not need to be synced. I think his method might have some range issues at the scale of redirected walking, though. If he sees this, he can correct me.

Last summer, I was working on a real time location system based off of VOR. The idea would be to use 2 phased-array antennas to transmit a stream of angular data in sync with a rotating peak amplitude signal. When client device detects the peak, it records the instantaneous angular value. With 2 such base stations, you can determine 2D absolute location, with 3 base stations (one being orthogonal to the others) you have 3D location. And the coolest part is that it in theory could work with any Wifi-enabled device with no additional hardware and support an indefinite number of users simultaneously. Got as far as determining which quadrant of the yard I was in using a can-tenna and a cheap RF receiver from Digikey, but there are two major blockers.

1. Phased-array antennas are expensive to buy, and non-trivial to make from scratch. Achievable with a lot of work, however.

2. I could not find any smart phones that exposed raw input amplitude without being connected to a network, which eliminates the fundamentally cool feature of the concept.

EDIT: Just searched again and found that the Android API might actually expose this information. Will have to revisit the idea some time...

FingerFlinger wrote:Krenzo's project may be a better solution for something like this, compared to terrestrial GPS. GPS is time-of-flight, which means that you need multiple base stations with highly-accurate and synced clocks. In his method, he's measuring the phase difference between 4 antennas on his sensor, so I think that the base stations do not need to be synced. I think his method might have some range issues at the scale of redirected walking, though. If he sees this, he can correct me.

My system doesn't have the range needed for a large outdoor area. To increase the range, you would use a carrier wave with a high bandwidth modulated signal. Unfortunately, if you were to use something like Wifi, your bandwidth would be limited by the channel bandwidth which is 22 MHz which would limit your spatial resolution. My system's bandwidth is around 2 GHz.

Krenzo wrote:My system doesn't have the range needed for a large outdoor area. To increase the range, you would use a carrier wave with a high bandwidth modulated signal. Unfortunately, if you were to use something like Wifi, your bandwidth would be limited by the channel bandwidth which is 22 MHz which would limit your spatial resolution. My system's bandwidth is around 2 GHz.

That's one of the reasons I don't think my idea would be particularly useful for VR. If I can implement it as purely as a software product on the client-side however, it could potentially work well as a commercial RTLS.

WARNING: This post describes uses and modifications of the Oculus Quest headset that are not recommended or sanctioned uses of the Quest hardware, software, or technology. Pursuing such uses or modifications may increase the risk of serious injury or property damage. If you try to replicate these or similar actions, you do so at your own risk.

My last update was over 6 years ago and it probably seemed like the project was dead, but I've got a new post today. In my last update I wrote
"just recently I accepted a job at Oculus (thanks again Palmer), so I'm going to be shutting down this project indefinitely to concentrate on my new job...
...I want to continue this research at some time in the future and my hope is that by surrounding myself full-time with VR technology and experts, I can develop a much better implementation."

So what has happened since then? Well, I'm still at Oculus having worked in a variety of areas and on loads of great projects, but I've had very little time to continue this locomotion hobby. After the first few Rovr iterations it became clear to me that some sort of dead-reckoning system was the only way to go - most likely either an inertial or a computer vision system. At first I focused on an inertial suit because it felt like the easier solution to implement. I backed the PrioVR Kickstarter in hopes that I could get a ready-made suit but that project failed, so I tinkered a little with building my own IMU pants but couldn't really find the time or motivation, especially since I felt the system would be compromised by drift and accuracy. What I really wanted was a computer vision system but it was out of my technical comfort zone. I had hoped to join the computer vision group at Oculus to acquire the skillset to work on it, but that move never materialized so the project remained on ice - or almost. For each headset iteration I would retrofit the previous Rovr. I made a DK1, a DK2, and a CV1 upgrade of the original IMU/GPS system just for fun, but the performance never really improved and nothing interesting really came of it.

Then the Santa Cruz project started to come together. This was exactly what I had been waiting for and I didn't have to do anything - just wait for others to solve all the hard problems. I was a little skeptical that the tracking performance would scale but even early versions far exceeded my expectations, so once Quest started to reach a mature state I finally sat down to implement an improved version of redirected walking. The video above shows the results. Conceptually it's identical to the previous Red Rovr but the precision and latency are orders of magnitude better. The older version was essentially a gesture system. You had to move with exaggerated intent to start a delayed glide and then align your walking speed with the character in order to achieve a sense of agency and presence. The Quest version just works. You move through the world naturally without conscious effort or compromise and the longer you go, the more transported you feel. Except for the non-engaging content shown above, this is the most pure and immersive type of VR experience available.

I used a stock Quest headset and 2 decks of playing cards thrown randomly on the ground to provide some visual contrast for tracking. The Quest is not recommended and does not work well outdoors, but I filmed on a fully overcast day to avoid camera saturation and potential damage and also to allow for some controller tracking. Under these conditions headset tracking works, but controller tracking was only viable for basic operation.

The redirection algorithm is bare-bones and largely unchanged. It simply tracks the clock direction of motion relative to the field center and rotates the virtual world around the player in the same direction. There are a variety of tricks to accomplish tighter redirection in specialized scenarios but I have always been interested in the worst-case: continuous exploratory movement through non-customized content. For that scenario this example field size of 40m x 40m is a bit small. I used a 4 deg/sec turning speed here and still hit the boundary more frequently than I would consider acceptable. For me 4 deg/sec is still perceptible and others that have tried it commented that it made them feel slightly drunk. So I still agree with my findings from earlier versions: 2 deg/sec feels optimal and likely a field size from 60m^2 to 80m^2 is ideal to avoid frequent edge collisions. This all seems technically possible with the Quest, but it does make finding a play space more challenging. Again, this is for the most challenging case - imperceptible redirection during continuous motion. Distracting content or content that encourages slower more deliberate motion (ie. indoor worlds) can work in smaller play spaces and there is a body of research that covers all of these variances and specialized techniques. https://illusioneering.cs.umn.edu/paper ... ga2018.pdf
But I would still not suggest that basketball courts are sufficient (much less a large room) for a great experience.

One big improvement is the new boundary enforcement - a custom system implemented in-app after disabling the Oculus Guardian. My previous boundary enforcement attempted to quickly spin the world to bring you back into the play-field, but that had the disadvantage of not giving environmental context and also producing discomfort. The new one works like other guardian systems in that it displays your real-world boundaries once you get close to the edge (the red zone). But within the red zone it also face-locks the virtual world to your head direction. That allows you to quickly turn the world to align better with your real boundary and start moving again in an optimal direction. The optimal direction is rarely towards the center of the field but instead lies along a shallow angle entering back into the play-field. This tangential path will tend to send you along a circle around the field center. To avoid discomfort and dizziness associated with face-locking, a full boundary floor is rendered during turn correction to give you a stable ground reference.

All-in-all I am satisfied with this system and it's pretty much what I had envisioned long ago when I started this thread. I'm closing this project now since there seems little reason to pursue an external redirection system when it's so easily achieved now with a couple hundred lines of code onboard an integrated $400 headset and 5 minutes of setup. That's probably the most shocking realization to me - the incredibly low cost and ease of this experience now. Even two years ago an experience with this scale and fidelity would have cost 100's of thousands of dollars and weeks of setup to achieve. The speed of progress that VR has undergone in the last 7 years is amazing and I feel incredibly lucky to have been a participant and first-hand witness to the rebirth and progression of VR.

Last edited by brantlew on Fri Aug 16, 2019 12:11 pm, edited 1 time in total.

The “directions” for exploration here are ripe with opportunity. Accelerated head turning, distractions to slow the user down, vection optical illusions, etc. could get you to a really solid system. Heuristics to avoid multiple people bumping into each other, and a companion phone-app that corrects the Quest with GPS/Compass while also providing a WiFi hotspot for multiplayer would make this almost a consumer product!

You simply can’t buy the ability to explore a dungeon, fight a dragon, or jog through Skyrim with several of your closest friends any way else...

If I didn’t live deep in SF (without easy access to open spaces), I’d be tempted to build a Unity plugin for it...